Mine roof supports



' April 1966 J. D. KIBBLE ETAL 3,246,576

MINE ROOF SUPPORTS Original Filed Oct. 7, 1960 4 Sheets-Sheet 1 FIG. 2.

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April 19, 1966 J. D- KIBBLE ETAL MINE ROOF SUPPORTS 4 Sheets-Sheet 5 Original Filed 0st. 7, 1960 e e m 02% April 1966 J. D KIBBLE ETAL 3,246,576

MINE ROOF SUPPORTS Original Filed 001;. 7. 1960 4 Sheets-Sheet 4 United States Patent M 3,246,576 MINE ROOF SUPPORTS .Iohn Eunbar Kibble, London, and Ronald George Penn,

Hounsiow, England, assignors to Coal Industry (Patents) Limited, London, England @riginal application Get 7, 1960, Ser. No. 61,210. Divided and this application Feb. 6, 1964, Ser. No. 342,874 Claims priority, application Great Britain, June 16, 1960,

,211/69 18 Claims. (Ci. 91-189) This application is a division of patent application Serial No. 61,210, filed October 7, 1960.

The present invention relates to mine roof support systems and particular to systems for supporting the roof of a longwall mineral face, for example a longwall coal face.

According to the invention, we provide a mine roof support system which comprises a plurality of extensible and retractable pressure fluid operated mine roof support adapted to be advanced in a predetermined sequence and arranged at spaced intervals along a longwall mineral face, and further comprises control means mounted on each support for controlling the cycle of lowering, advancing, and resetting operations of the support, said control means including initiating means adapted auto matically to initiate the said cycle and check means having a clear condition and a stop condition and adapted to be automatically placed in the clear condition when the support has completed the said cycle of operation, connection means arranged to connect the control means for one support to the control means for the next support in the sequence to be advanced, the check means on one support, the connection means, and the initiating means on the next support in the sequence to be advanced being directly connected in series so that upon the said check means being placed in a clear condition an unbroken signal path exists between the control means for said one support and the initiating means for said next support in the sequence to be advanced, whereby the cycle of operations for said next support is only initiated upon completion of the cycle of operations of said one support.

Four specific and illustrative embodiments of the invention will now be described with reference to the accompanying drawings, in which:

FIGURE 1 and FIGURE 2 are partly diagrammatic side and end elevations respectively of the structure of one mine roof support, a plurality of which constitute a system according to the present invention,

FIGURE 3 is a diagram of a hydraulic circuit of one support in a first embodiment of the invention,

FIGURE 4 is a diagram of an electrical circuit used in conjunction with the hydraulic circuit shown in FIG- URE 3,

FIGURES 5, 6, and 7 are respectively diagrams of the hydraulic circuit of one support in second, third, and fourth embodiments of the invention,

FIGURE 8 is a diagram of an electrical circuit used with either of the hydraulic circuits shown in FIGURES 5 and 6, and

FIGURE 9 is a diagram of an electrical circuit used with the hydraulic circuit shown in FIGURE 7.

In FIGURES 1 and 2 is shown a hydraulic self-advano ing mine roof support unit which is one of a plurality (the others not being shown) linked to an armoured flexible face conveyor.

FIGURE 1 is a view in a direction parallel to the coal face, and FIGURE 2 which is an end elevation at right angles to the coal face looking towards the unexcavated coal. The unit consists of a base 1 upon which are mounted resiliently two single acting hydraulic jacks, 2 and 3,

3,246,576 Patented Apr. 19, 1956 which will be termed legs. A roof bar 4 is mounted, also resiliently, upon the legs 2 and 3. Within the base 1 a double-acting hydraulic cylinder 5 is mounted in a gimbal bearing 6 which permits a limited amount of angular movement of the cylinder 5. The piston rod 7 of the cylinder 5 is connected by means of a pin 8 and a bracket 9 to the armoured flexible face conveyor 10. The con veyor carries a spill plate 11 upon which are mounted at intervals brackets 12 which carry the flexible pipes 13 passing along the length of the face. The pipes 13 are connected to each support unit by branch flexible pipes as may be required. A hydraulic valve block 14 is mounted in a suitable position on the base. This is connected with the cylinder 5 and the legs 2 and 3 by pipes which are not shown. Similar support units are placed at short intervals throughout the length of a longwall coal face.

The manual operation of this will now be described. After a Web of coal has been cut and loaded on the conveyor hydraulic pressure is applied to the cylinder 5 in such a way as to cause the rod 7 to be pushed out. At the same time the other support units are operated similarly. This will cause the conveyor to move forward into the space vacated by the cut coal. It may only be necessary to push the conveyor with the cylinder of a proportion of the support units. The support units are then moved forward one at a time in sequence along the face by means of lowering the legs of each, and reversing the hydraulic pressure connections to the cylinder 5 so that the rod 7 is pulled in. As the conveyor will be held in position by the pushing action of adjacent support units this operation will cause the support unit in question to move forward until its cylinder 5 is fully contracted. Hydraulic pressure is then re-applied to the legs 2 and 3 so that they extend until the roof bar 4 is forced against the roof. The hydraulic connections to the cylinder 5 are then reversed so that it resumes pushing against the conveyor. The next support unit may then be lowered, advanced and reset similarly, but it is imperative for reasons of safety that no unit is lowered from the roof unless the adjacent one has been reset.

The means by which these operations may be performed without manual intervention is shown in FIG- URE 3, which is a diagram of the fluid pressure operated equipment of one support unit of the many units which in practice form a complete sequence of units arranged along the mineral face. In FIGURE 3 the legs of the support unit are shown at 2 and 3 and its horizontal cylinder at 5. The necessary valves may be constructed in one block represented by the chain-dotted line 15. The flexible pipe running along the face conveying hydraulic fluid from the pump is shown at 17 and that returning fluid to a tank (not shown) at 18. An additional flexible pipe 19 is also required.

In the normal state of the circuit only the pipe 17, has fluid pressure applied to it. This pressure is fed through a non-return valve 21 to a leg control valve 22, which is a 3-ported two-position valve spring loaded into the position shown in which the hydraulic pressure is allowed to pass through the connection 23 to the legs 2 and 3. If convergence of the roof should take place the fluid contained in the legs 2 and 3 cannot return to the line 17 because of the action of the valve 21. The pressure is therefore built up until it is sufficient to operate a relief valve 2% through which the fluid escapes to a reservoir 01' to waste.

The cylinder 5 is controlled by means of a valve 25, which is a 5-ported two position valve normally held by a spring in the position shown in which the pump pressure, though applied to port 26 of the valve 25, is there sealed off. In a similar manner the pressure of the pipe 17 is applied to the legs 2 and 3 of the other supports in the 5., sequence so that except when a support is actually being caused to advance it is automatically held in its roof supporting position.

When it is desired to advance the conveyor, pressure is applied to the pipe 19, and the valve 25 allows this pressure to pass through to the end 27 of the cylinder to cause extension of the piston rod 7. The purpose of the separate pressure line 19 is to permit control of the pressure with which the conveyor is advanced, as is required for certain mining operations such as the use of coal'ploughs. If this is not desired the port 28 may be connected to the main pressure line 17 instead of to the pipe 19.

When it is desired to advance the roof supports in sequence, an electrical signal is applied to solenoids 65 and 70 (see FIGURE 4) of electrohydraulic valves 50 and 51 of the first unit to be advanced by means of the key or switch 62. Returning now to FIGURE 3, the valves 50 and 51 are three-ported two-position valves and are spring loaded into the positions shown in FIGURE 3, herein referred to as first position. In these first positions the pilot cylinders 29 and 31 of valves 22 and are connected to the return line 18 through ports 52 and 53 of valves and 51 but when the valves 50 and 51 are energised they move to a position hereinafter referred to as second position in which the pilot cylinders 29 and 31 are connected through ports 52 and 54 to the pressure line 17 by conduit 55.

The pressure applied to cylinder 29 of valve 22 moves it to its second position in which the legs 2 and 3 are disconnected from the pressure line 17 and connected to the return line 18, thus permitting the legs 2 and 3 to lower.

The pressure applied to the cylinder 31 of the valve 25 causes the valve to move to its second position in which the pushing side 27 of the cylinder 5 is connected through the port 32 of the valve 25 to the return line 18; the port 28 is sealed to cut oif the pressure supplied by the line 19; and also the other end 33' of the cylinder 5, previously connected through the ports 34 and 32 of valve 25' to the return line 18 is then connected through the port 26 to the pump pressure in the main pipe 17.

Therefore, at the same time the legs are lowered from the roof and the support unit is brought forward.

There is provided in the path of a projection 56 carried by the piston rod of the cylinder 5, a transducer in the form of a limit switch 57 actuated to give an electrical output upon the cylinder 5 fully advancing the support unit. The inter-relation of the valve 50 and the limit switch 57 can be seen in FIGURE 4. In this figure it can be seen that the limit switch comprises two coupled contacts 58 and 59 in series respectively to leads 60 and 61 connected through a switch 62 to one side of a power supply 63. The other side of the power supply 63 is connected by lead 64 common to all the solenoid valves 50, 51 of the units of the system to one end of the coil 65 of the valve 50 the other end of which is connected, upon closure of the contact 58 to the lead 60.

The contact 59 of the limit switch 57 is connected in series by lead-66 with one contact 67 of a pressure switch 68 which (as can be seen in FIGURE 3) is connected to the hydraulic circuit of the legs 2 and 3 and is operated upon the pressure in that circuit reaching a value indicative that the legs are adequately set. The pressure switch 68 is, similar to switch 57, provided with two contacts and the other contact 69 is in series with the coil 70 of valve 51. Closure of contacts 59 and 67, it will be seen, connects lead 71 to the power supply 63 through switch 62.

Closing switch 62 will energise the coils 65 and 70 (through contacts 58 and 69 respectively) and the valves 50 and 51 are moved to operate the hydraulic circuit of FIGURE 4 as above described.

However, when the support unit is fully advanced, the limit switch 57 will be operated by projection 56 such .A' that the contact 58 is opened and the valve 50, therefore, de-energised so that it returns (under the action of its spring) to the position shown in FIGURE 3.

In this position of the valve 50, the pilot cylinder 29 of valve 22 is re-connected to the return line 18 (through ports 52 and 53 of valve 50) and the valve 22 restored by its spring to its initial position in which the legs are pressurised by line 17 through valves 22 and 23.

When the pressure in the legs 2 and 3 reaches a value indicative of their being adaquately set against the roof, the pressure switch 68 operates to move its contacts from the position shown in FIGURE 3 into the position in which the supply of current to the coil 70 of valve 51 is cut-off (by opening of contact 69) and (by closing of contact 67) current to initiate operation of the next succeeding support is passed to that support over lead 71, this current energising the valves 50 and 51 of the next succeeding support.

This arrangement of FIGURES 3 and 4 shows the electrical circuit of the supports arranged in series along the face but, if desired, this arrangement may be modified by referring bac to a control'panel the electrical connections to the solenoid valves and to limit switch and the pressure switch. There is then the great advantage of being able, from the control point, to observe the position and leg pressure of each support unit and of being able to control each operation individually if desired.

The system has, however, the disadvantage of requiring two solenoid valves per support'unit. This may be expensive and, particularly, it may prevent the use of intrinsically safe electric circuits as the power required may be too high.

These disadvantages can be avoided by the use of either F of the circuits shown in FIGURES 5 and 6.

Referring to FIGURE 5, the diagram includes the double-acting horizontal hydraulic ram comprising a cylinder 5 accommodating a piston rod 102 connected pivotally to an armoured flexible face conveyor (not shown). Two legs 2 and 3 of the roof support unit are indicated, but it w-ill be realised that each such unit may comprise any desired number of legs, Extending along the length of the face are a main pressure flexible hose 17, a return flexible hose 18, and a conveyor advancing-pressure flexible hose 19. A hydraulic valve block schematically illustrated by a chain-dotted rectangle 15 is connected to both ends of the cylinder 5 and'to'the legs 2 and 3 and to the flexible :hoses 17, 18 and 19 by flexible branch pipes indicated by double lines. A- solenoid operated valve 103 is connectedinan appropriate-electrical circuit shown in FIGURE 8, the circuit also including a limit switch 57 and a pressure switch 68 whose functions are similar to the equivalent switches shown in FIGURE 4. The control arrangement also comprises a hydraulic leg control valve 22, a hydraulic ram control valve 120, a hydraulic leg relief valve 24 and a non-return valve 21.

The various valves 103, 22, 120, 24 and 22- may either be formed in internal passages of the block 15 or they may have separate bodies mounted on block 15.

The solenoid valve 103 is of similar construction as the valve 50 or 51 of FIGURES 3 and 4 and controls the application of a pilot pressure to the hydraulic valve 22 and 120. The-valve 103 is a two-position, three-ported valve, and in its normal dc-energised state, the output port 52 is connected to the return port 53 and the input port 54 is blocked. On the solenoid becoming energised, the valve 103' operates solthat the input port 54" is connected to the output port 52 and the return port 53 becomes blocked. This then allows a' pilot pressure from line 17 to be applied to the pilot cylinders 29 and 121 of the hydraulic valves- 22 and 1201 The hydraulic leg control valve 22, which controls the raising and lowering of the legs 2 and 3 and also returns the hydraulic valve to its normal position, is a twoposition valve with three main ports and one pilot port.

In the normal position of the valve 22 the input port 104 is connected to the output port 105 and thence to the legs 2 and 3, and also to a pilot port 106 of the hydraulic valve 120. On applying a pilot pressure to the pilot cylinder 29, the valve 22 operates so that the input port 104 becomes blocked and the output port 105 is connected to a return port 107. This allows the pressure in the legs 2 and 3 and the pressure of pilot port 106 on hydraulic valve 120 to be released. On releasing the pilot pressure from pilot cylinder 29, a spring 108 returns the valve 22 to its normal position.

The hydraulic ram control valve 120 which controls the action of the double-acting cylinder 5, is a two-position valve with five main ports and three pilot ports. In its normal position the conveyor advancing pressure input port 109 is connected to the output port 110 and thence to the pushing port 111 of the cylinder 5. At the same time, the pulling port 112 of the cylinder 5 is connected to the return port 113, via the output port 114. On applying a pilot pressure to the pilot cylinder 121, the valve 120 operates (so long as pressure is not applied to pilot port 105 at the same time) so that the conveyor advancing pressure input port 109 becomes blocked and the output port 110 is connected to the return port 113. This will stop the pushing forward of the face conveyor. At the same time the main pressure input port 115 is connected to the output port 114 and thence to the pulling port 112 of The cylinder. This allows the roof support unit to be pulled forward. The output port 114 is also connected to the pilot port 116. This allows the valve 5 to be kept in its operated position after the pilot pressure at pilot cylinder 121 has been released. This is known as self-holding. The valve 120 will remain in its operated position until the pressureat the pilot port 106 creates a force great enough to overcome that due to pressure at the pilot port 116. The valve 120 will then return to its normal position.

The electrical circuit of the above described apparatus is shown in the accompanying FIGURE 8 and includes in addition to the coil 122 of the valve 103 a limit switch 5'7 similar .to the limit switch 57 of FIGURE 4 and a pressure switch 68 similar to the pressure switch 68 of FIG- URE 4 but having only a single contact 123 instead of the double contacts 67 and 69.

The operation of the whole circuit can now be described. With the valves 103, 22 and 120 in their normal position, it can be seen that the conveyor advancing pressure from the hose 19 is applied to the pushing port 111 of the cylinder 5 and that the main pressure from the hose 1? is applied to the legs 2 and 3 and to the pilot port -6 of the hydraulic valve 120. When it is desired to move the roof support unit forward, the solenoid valve 103 is energised by closing switch 62 (FIGURE 8). On becoming energised, the solenoid valve 103 supplies a pilot pressure to the pilot cylinder 29 of the leg control valve 22 and to the pilot cylinder 121 of the ram control valve 120. This pilot pressure operates the leg control valve 22 which releases the pressure from the legs 2 and 3 and also from the pilot port 106 of ram control valve 120. The ram control valve 120 now operates, which allows the main pressure to flow to the pulling port 112 of the cylinder 5, and this will pull the roof support unit forward. After the roof support unit has moved forward to its required position, the limit switch 57 (FIGURE 8) is operated so that the solenoid valve 103 is ale-energised by the opening of contact 58 of switch 57. This allows the leg control valve 22 to return to its normal position and thus re-apply pressure to the legs 2 and 3. The ram control valve 120 remains in its operated position, because of its self-holding feature on pilot port 110 and continues to give the cylinder 5 a pulling force until the legs 2 and 3 come into contact with the roof. As the legs 2 and 3- come into contact with the roof, pressure at pilot port 106 of the ram control valve 120 builds up and returns the ram control valve to its normal position i.e. supplying conveying advancing pressure from line 19 to the pushing port 111 of the cylinder 5.

Because of the non-return valve 21, which is positioned before the leg control valve 22, the main pressure 17 can be switched off without the legs 2 and 3 lowering. On roof convergence taking place, excess pressure in the legs 2 and 3 is bled to atmosphere by the leg relief valve 24.

When the legs 2 and 3 are fully set against the roof, the pressure in the hydraulic circuit of the legs operates the pressure switch 68 such that its contact 123 is closed. As the contact 59 of the limit switch 57 has also previously been closed (by operation of the limit switch 57 upon the support unit being moved forward to its required position), the current through switch 62 (i.e. from source 63, FIGURE 4) will be passed to the next support unit to be operated such as to energise its solenoid valve 103 and thereby initiate operation of the support. It will be seen, therefore, that the operation of the next support is only initiated when it is proved that the legs 2 and 3 of the pre ceding support has been fully set and that the preceding support has been fully advanced.

In an emergency, the system can be controlled manually by the manual operation screws 46 and 47. Operation of the manual operation screw 43 on the leg control valve 22 will lower the legs 2 and 3, thus allowing the support to move back if desired. Operation of the manual operation screw 47 on the ram control valve 120 will allow the roof support unit to be moved forward or the face conveyor to be moved back, depending upon the position of the leg control valve 22.

A further alternative embodiment of the invention can be used in the operating conditions at a plough face as shown in FIGURE 6. In this circuit the ram control valve 120 in FIGURE 5 has been replaced by a ram push control valve and a ram pull control valve 131. The operations of the solenoid valve 103 and the leg control valve 22 are the same as described above for FIGURE 5.

The ram push control valve 130, which controls the pushing action of the cylinder 5 is a two-position valve, with three main ports and two pilot ports. In normal position (i.e. the position shown) of the valve 130 the return port 113 is blocked and the input port 109 is connected to the output port 110 and thence to the pushing port 111 of the cylinder 5. When the pressure from pilot port 132 is released, the valve 130 operates due to the main pressure always being applied to pilot port 133. In the operated position of the valve 130 the input port 109 is blocked and the output port 110 is connected to the return port 113. This will stop the pushing forward of the face conveyor. The valve 130 will remain in its operated position until the pressure at the pilot port 132 creates a force great enough to overcome that due to pressure at the pilot port 133. The valve 130 will then return to its normal position.

The ram pull control valve 131 which controls the pulling action of the cylinder 5, is a two-position valve, with three main ports and one pilot port. In the normal position (i.e. the position shown) of the valve 131 the output port 114 is connected to the return port 134 and the input port 135 is blocked. 011 applying a pilot pressure to the pilot port 136, the valve 131 operates so that the return port 134 is blocked and the input port 135 is connected to the output port 114 and thence to the pulling port 112 of the cylinder 5. On releasing the pilot pressure form pilot port 136, a spring returns the valve 131 to its normal position.

The operation of this circuit of FIGURE 6 can now be described, referring to FIGURES 6 and 8. With the valves 103, 22, 13-0 and 131 in their normal position, it can be seen that the conveyor advancing pressure from the hose 19 is applied to the pushing port 111 of the cylinder 5 and that the main pressure from the hose 17 is I? applied to the legs 2 and 3 and to the pilot port 132 of the hydraulic valve 139.

When it is desired to move the roof support unit forward the solenoid-operated valve 193 is energized in the manner described above and illustrated with reference to FIGURE 8. On becoming energized, the solenoid valve 103 supplies a pilot pressure to the pilot cylinder 29 of the leg control valve 22 and to the pilot port 136 of the ram pull control valve 131. This pilot pressure operates the leg control valve 22 which releases the pressure from the legs 2 and 3 and also from pilot port 132 of the ram push control valve 139, thus allowing the ram push control valve 130 to operate. This stops the pushing action of the cylinder 5 and the ram pull control valve 131, which is now in its operated position, due to pilot pressure at pilot port 136, allows the main pressure to flow to the pulling port 112 of the cylinder 5, and this .pulls the roof support unit forward. When the roof support unit has moved forward to its required position, the limit switch 57 (FIGURE 8) is operated such that the solenoid valve 193 is de-energized, and this allows the leg control valve 22 and the ram pull control valve 131 to return to their normal positions. The pulling action of the cylinder 5 now ceases, and the main pressure from the hose 17 is re-applied to the legs 2 and 3 and also to the pilot port 132 of the ram push control valve 130. As the legs 2 and 3 came into contact with the roof, pressure at the pilot port 132 creates a force larger than that due to pressure at the pilot port 133 of the ram push control valve 130. This valve 130 now returns to its normal position, thus allowing a pushing action to be reapplied at cylinder 5.

The operation of the attendant electrical circuit (which is identical to that shown in FIGURE 8) is the same as described above with reference to the embodiment of the invention illustrated in FIGURES 5 and 8. That is to say, when the support is proved fully set and the support proved fully advanced, operation of the next succeeding support is initiated automatically.

The functions of the non-return valve 21 and the leg relief valve 24 are the same as described above for the circuit in FIGURE 5.

This system of FIGURE 6 can also be controlled manually in an emergency by the manual operation screws 46, 137 and 138.

Operation of the manual operation screw 46 on the leg-control valve 22 will lower the legs 2 and 3. At the same time it will cause the pushing action of the cylinder 5 to cease if the main pressure at line 17 is switched on. If the main pressure at line 17 is switched oft" it will cause the roof support unit to move back.

Operation of the manual operation screw 137 on the ram. push control valve 130 will stop the pushing action of the cylinder 5.

Operation of the manual operation screw 138 on the ram pull control valve 131 will move the face conveyor back if the manual operation screw 137 is also operated at the same time. Operation of the manual operation screw 13% will also move the roof support unit forward it the legs 2 and 3 are released.

The circuit to be now described with reference to FIGURE 7 is particularly suitable for installations rcquiring snaking of the conveyor.

In FIGURE 7 is indicated a horizontal hydraulic ram comprising a cylinder 5 accommodating a piston rod 162 which is pivotally connected to an armoured flexible face conveyor (not shown). Also indicated are two legs 2 and 3 of a roof support unit but, again, any desired number of such legs may be provided. A main pressure flexible hose 17 and a return flexible hose 18 extend along the face. The arrangement also comprises a solenoid-operated valve 140 for leg control and ram pull control, a ram push control solenoid-operated valve 141, a hydraulic leg control valve 142, a hydraulic ram pull control valve 143, a hydraulic ram push control valve 144, a hydraulic leg relief valve 24, a non-return valve 21, and a hydraulic valve block 15 which is connected to both ends of the cylinder 5 and to the legs 2 and 3 and to the flexible hoses 17 and 18 by means of flexible branch pipes indicated by single lines.

The valves to 144 and valves 21 and 24 may either be formed in internal passages of the block 15 or they may have separate bodies mounted on block 15.

The solenoid-operated valve 140 which controls the application of a pilot pressure to the hydraulic valves 142 and 143 is a three-ported, two-position valve and functions in the same way as the solenoid-operated valve 103 in FIGURE 6, i.e.,

Normal tie-energized state: Input 54 blocked, output 52 connected to return 53.

Operated position: Return 53 blocked, input 54 connected to output 52.

The solenoid valve 141, which controls the application of a pilot pressure to the hydraulic valve 144 is also a three-ported, two-position valve and functions in the same way as the solenoid-operated valve 145, the input port being 145, the output port 146 and the return port 147. The reason for having this second solenoid-operated valve 141 will be stated further on.

The hydraulic leg control valve 142, which in this case only controls the raising and lowering of the legs 2 and 3, is a two-position valve with three main ports and one pilot port 148. It functions in the same way as the leg control valve 22 in FIGURE 5, i.e.,

Normal position: Return 149 blocked, input 159 connected to output 151.

Operated position: Input 150 blocked, output 151 connected to return 149.

The hydraulic ram pull control valve 143 which controls the pulling action on the cylinder 5 and also returns the ram push control valve 1 .4 to its normal position is a two-position valve with three main ports and one pilot port 152. It functions in the same way as the ram pull control valve 131 in FIGURE 6, i.e.,

Normal position: Input 153 blocked, output 154 connected to Return 155.

Operated position: Return 155 blocked, input 153 connected to output 154.

The hydraulic ram push control valve 144 controls the pushing action of the cylinder 5 and is a two-position valve with three main ports and three pilot ports. In its normal position the input port 156 is blocked and the output port 157 is connected to the return port 158. On applying a pilot pressure to pilot port 15%, the valve operates (so long as pressure is not applied to pilot port at the same time) so that the return port 153 becomes blocked and the input port 156 is connected to the output port 157 and thence tothe pushing port 111 of the cylinder 5. The output port 157 is also connected to the pilot port 159. This connection allows the valve 144 to be kept in its operated position after the pilot pressure at pilot port 159a has been released. (This is known as self-holding) The valve 144 remains in its operated position until the pressure at pilot port 1166 creates a force great enough to overcome that due to pressure on pilot port 159a; the valve 144 then returns to its normal position.

The electrical circuit for the embodiment shown in FIGURE 7, is shown in FIGURE 9. As can be seen from FIGURE 9 the circuit incorporates the coils 160 and 161 respectively of solenoid valves 14% and 1.41, a limit switch 57 having contact 58 and 59 which is similar to and performs the same function as switch 57 of FIGURES 4 and 8, a pressure switch 68 which has a single contact 123 and which is similar to and performs the same function as the pressure switch 68 of FIGURES 4 and 8, and a main switch 62 controlling the supply of power from source 63. The circuit also includes a selector switch 9 162 by means of which any one of the solenoid valves 141, or none, may be energised.

The operation of the whole circuit shown in FI URES 7 and 9 can now be described. With the valves 140 to 14-4 in their normal position, it can be seen that the main pressure from the hose 17 is applied to the legs 2 and 3.

When it is desired to snake the conveyor the solenoidoperated valve 141 is energised by setting of the selector switch 162 to supply current to the coil 161. On becoming energised, the solenoid-operated valve 141 supplies a pilot pressure to the pilot port 159a on the ram push control valve 144. This pilot pressure operates the ram push control valve 144 thus allowing the main pressure from the hose 17 to how to the pushing side port 111 of the cylinder and push the face conveyor forwar Because of the self-holding feature of the ram push control valve 144, the solenoid-operated valve 141 may be de-energised once the face conveyor starts to move forward.

When the face conveyor has been moved forward to its required position, the solenoid-operated valve 14% is energised by closing switch 62. On becoming energised the solenoid-operated valve 140 supplies a pilot pressure to the pilot port 148 of the leg control valve 142 and to the pilot port 152 of the ram pull control valve 143. The leg control valve 142 operates, thus releasing the pressure from the legs 2 and 3. The ram pull control valve 143 also operates thus supplying a pilot pressure to pilot port 160 of the ram push control valve 144, which now returns to its normal position. The main pressure from the hose 17 now flows to the pulling port 112 of the cylinder 5 and the roof support unit moves forward.

After the roof support unit has moved forward to its required position, the solenoid-operated valve 140 is deenergised by opening of the contact 58 upon actuation of the limit switch 57 when the support reaches its fully advanced position. This now allows the leg control valve 142 and the ram pull control valve 143 to return to their normal positions. The pulling action of the cylinder 5 now ceases and the main pressure from line 17 is reapplied to the legs 2 and 3.

The use of the non-return valve 21 and the leg-relief" valve 24 is the same as that described above for the circuit in FIGURE 3.

When the limit switch 57 is operated upon the support being fully advanced, not only is contact '53 opened but also contact 57 is closed. Further when the pressure switch 68 is operated upon the legs 2 and 3 becoming fully set against the roof, current is then passed to the coil 3.60 of solenoid valve 140 of the next support. With the energisation of this valve, the operation of the next succeeding support will be initiated.

In an emergency the system shown in FIGURE 7 can be controlled manually by the manual operation screws 163, 164 and 1%.

Operation of the manual operation screw 163 of the leg control valve 142 will lower the legs 2 and 3.

Operation of the manual operation screw 164 of the ram pull control valve 143 will either move the support forward or pull the face conveyor back, depending upon the position of the leg control valve 142.

Operation of the manual operation screw 165 of the ram push control valve 143 will either push the face conveyor forward or move the roof support unit back, once again depending on the position of the leg control valve 142.

It is found that on a coal face where this type of circuit (FIGURES 7 and 9) is required, a number, of the roof support units are requiredto push the face conveyor forward at the same time after the coal cutter has passed them. It is found that a sufiiciently powerful solenoid-operated valve for these circuits takes so much current, that only one may be energised at a time in an intrinsically safe circuit. It is for this reason that self-holding valves are employed for ram-push control. Alternatively, use may be made of a slide valve with no return spring, or any other type of valve possessing the characteristic that, upon the application of fluid pressure to one of its pilot ports, it will move from the first of its two positions to the second and remain in that position after the removal of that fluid pressure, being restorable to its first position by the application of fluid pressure to another pilot port.

As already mentioned, the solenoid valve 141 may be de-energized as soon as the roof support unit starts to move the face conveyor forward. This then allows for another solenoid-operated valve 141 to be energised and tie-energized on another roof support unit, and so on in sequence along the face. On a face with such roof support units it is not always required for every roof support unit to have a double-acting cylinder 5, perhaps only every fourth roof support unit will need such a double-acting cylinder. This being so, the solenoid-operated valve 141 can be removed and replaced by a blanking plate when only a pulling action is required from the cylinder 5.

If it is required not to have the front legs and the rear legs of a roof support unit connected to the same hose, the leg control valve can be replaced by either:

(i) A front leg control valve and a rear leg control valve, or

(ii) A leg raise control valve and a leg release contro valve with a system of non-return valves.

These two alternative leg circuits apply to the arrangements shown in any of FIGURES 5-7.

The pressure drops in the hydraulic circuits during operating cycles will obviously depend upon the characteristics of the components involved. It is to be understood that, if convenient, restrictors may be inserted at various points in the hydraulic circuits to obtain the sequence of operations described.

The limit switches 57 shown in FIGURES 4, 8 and 9 may be replaced by position transducers that is to say, electrical devices having one part which can move relative to another part and whose output is dependent on the relative positions of the parts, one of the parts being mounted on the cylinder 5 and the other being mounted on or attached to the piston rod 102. Such position transducers are of known construction and are capable of giving an electrical output proportional to the extension of the ram. Such position transducers may be used with an electrical circuit of any of a number of known kinds having the characteristic that a relay ope-rates when the electrical input reaches a predetermined value. Preferably this value is adjustable. The relay has contacts corresponding to the contacts 58 and 59 of the switch 57. By suitable adjustment the relay may then be made to operate when the support unit reaches the end of its advancing travel, or, if desired, when it reaches any other position.

Similarly, the pressure switches 68 may be replaced by proportional pressure transducers used in conjunction with an electric circuit having a relay with contacts corresponding to the contacts 67 and 69 or, as may be required, one set of contacts corresponding to those 123. By proportional pressure transducer herein is meant a pressure-voltage, pressurecurrent, or pressure-other electrical characteristic transducer having the property that it gives an output electrical voltage, current, or other characteristic which is linearly dependent on the input pressure. Such transducers are known and their specific construction forms no part of the present invention.

We claim:

1. A mine roof support system comprising a plurality of extensible and retractable pressure fluid operated mine roof supports adapted to be advanced in a predetermined sequence and arranged at spaced intervals along a longwall mineral face, and further comprising control means mounted on each support for controlling the cycle of lowering, advancing, and resetting operations of the support, each said control means including initiating means adapted automatically to initiate the said cycle and cheek means having a clear condition and a stop condition and adapted to be automatically placed in the clear condition when the support has completed the said cycle of operation, connection means arranged to connect the control means for one support to the control mean for the next support in the sequence to be advanced, the check means on one support, the connection means, and the initiating means on the next support in the sequence to be advanced being directly connected in series so that upon the said check means being placed in a clear condition an unbroken electrieal signal path exist between the control means for said one support and the initiating means for said next support in the sequence to be advanced, whereby the cycle of operations for said next support is only initiated upon completion of the cycle of operations of said one support.

2. A mine roof support system comprising a plurality of extensible and retractable pressure-fluid operated mine roof supports adapted to be advanced in a predetermined sequence and arranged at spaced intervals along a longwall mineral face, a control means mounted on each support including a plurality of hydraulic valves, an electric circuit, at least one solenoid-operated electro-hydraulic valve having its solenoid in said electrical circuit, a switch in said circuit, and means responsive to fluid pressure in the support and adapted to close said switch when said fluid pressure exceeds a. pre-set value, each of said electro-hydraulic valves being adapted to initiate the lowering, advancing, and resetting operations of its respective support, and connection means including at least one electrical conductor extending along said mineral face and linking the electrical circuit of the control means on a given support with the electrical circuit of the control means on the next support in the sequence to be advanced, the said connectionmeans being arranged in relation to said solenoid and said switch such that upon the fluid pressure in said given support reaching said pre-set value, the switch is closed permitting an electrical signal from the preceding support in the sequence to be advanced to pass through the control means mounted on said given support to the solenoid of the electro-hydraulic valve in the control means mounted on the next support in the sequence to be advanced.

3. A mine roof support system according to claim 2 comprising a fluid-operable ram adapted to advance the support and trip means comprising a transducer mounted on the ram, said transducer adapted to give an electrical output upon a predetermined advance of the support and a relay having contacts arranged in series with the said connection means and being arranged to close upon the relay receiving said electrical. output, whereby saidelectrical signal from the preceding support in the sequence is permitted to pass to the next support in the sequence when said given support has made the said predetermined advance.

4. A mine roof support system according to claim 2 wherein said control means includes a first and a second hydraulic valve each having a first and a second position and an eleetrohydraulic valve having fluid connections to the first and the second hydraulic valve and arranged on receipt of said signal to pass pressure fluid to the first hydraulic valve to effect its operation from its first position to its second position, fluid conduits being provided between the first hydraulic valve and the corresponding support so that in the first position of the first hydraulic valve pressure fluid can. be supplied to the support and in the second position of the first hydraulic valve pressure fluid can be released therefrom.

5. A mine roof support system according to claim 4 including a double acting hydraulic ram for advancing the support wherein fluid conduits are provided connecting the second hydraulic valve and the said ram so that in the first and second respective positions of the second valve pressure fluid can be supp-lied and released in senses to extend and retract the ram respectively, and wherein a further fluid conduit to said second hydraulic valve is provided whereby said second hydraulic valve can be changed from its first position to its second position in response to said signal.

6. A mine roof support system according to claim 5 wherein said first and second hydraulic valves each include resilient means arranged to urge the valves towards their respective first positions.

7. A mine roof support system according to claim 2 wherein said control means includes two electrohydraulic valves each having a solenoid in series with said connection means and a first and a second hydraulic valve each having first and second positions, the arrangement being such that in the respective first and second positions of the first hydraulic valve pressurefluid can be respectively supplied to extend and release to contract the support, wherein a first fluid conduit is provided connecting one of said electrohydraulic valves to the first hydraulic valve so that upon the said electrical signal energising the solenoid of said one electrohydraulic valve, the first hydraulic valve is changed from its first to its second position.

8. A mine roof support system according to claim 7 comprising a double acting hydraulic ram for advancing the support wherein second and third fluid conduits are provided connecting said second hydraulic valve to the ram so that in the respective first and second positions of the second hydraulic valve pressure fluid can be supplied to and released from the ram in senses to extend and contract the ram respectively and wherein a fourth fluid conduit connects said sec-0nd hydraulic valve to the other of said two electrohydraulic valves whereby pressure fluid may be fed to a pilot chamber of the second hydraulic valve when said other electrohydraulic valve has its solenoid in an energised condition, said feeding of pressure fluid to said pilot chamber being effective to change said second hydraulic valve from its first to its second position.

9. A mine roof support system according to claim 8 including trip means comprising a transducer mounted on the ram, said transducer being adapted to give an electrical output upon a predetermined advance of the support and a relay having a first and a second pair of contacts, the first pair being arranged in series with said connection means and being arranged to close upon the relay receiving said electrical output, and the second pair being arranged in series with the solenoid of said one electrohydraulie valve and being arranged upon opening to deenergize the solenoid of said one electrohydraulic valve, the relay being such that one pair of contacts is open and one pair of contacts is closed in each of the energised and de energised conditions of the relay.

10. A mine roof support system according to claim 9 wherein the switch has two pairs of contacts, the first pair being arranged in series with said connection means and the second pair being arranged in series with the solenoid of said other electrohydraulie valve, the switch being such that one pair of contacts is open and one pair of contacts is closed in each of the operated and un-opcrated conditions of the switch, and the second pair of contacts when closed permitting energisation of the solenoid of said other electrohydraulic valve.

11. A mine roof support system according to claim 8 including a mechanical connection between said ram and a face conveyor and a fluid pressure supply conduit connected to the second hydraulic valve whereby in the first position of the second hydraulic valve fluid can be supplied to the ram to advance the conveyor.

12. A mine roof support system according to claim 3 comprising a solenoid operated electrohydraulic valve having its solenoid in series with said connection means, a support leg hydraulic control valve, a ram push hydraulic control valve, and a ram pull hydraulic control valve, each of the latter three valves having first and second positions, first fluid conduit means connecting the support and the leg valve whereby pressure fluid can be supplied to and released from the support in the first and second positions of the leg valve respectively, second and third conduit means respectively connecting the ram pull valve and the ram push valve with the fluid-operable ram, and a first fluid conduit connecting the electrohydraulic valve and the leg valve whereby when the solenoid of the electrohydraulic valve is energised, pressure fluid is passed through the electrohydraulic valve and effects changeover of the leg valve from its first to its second position.

13. A mine roof support system according to claim 12 wherein said second fluid conduit means permits exhaust of fluid from the ram upon its extension when the ram pull valve is in its first position and permits supply of fluid to contract the ram when the ram pull valve is in its second position, and comprising a second fluid conduit connecting the electrohydraulic valve to the ram pull hydraulic control valve, whereby upon energisation of the solenoid of the electrohydraulic valve pressure fluid is passed through the electrohydraulic valve to the ram pull valve and effects change-over of the latter valve from its first to its second position.

14. A mine roof support system according to claim 13 wherein said third fluid conduit means permits supply of pressure fluid to extend the ram when the ram push valve is in its first position and permits exhaust of fluid from the ram upon contraction of the ram when the ram push valve is in its second position, and comprising a third fluid conduit connecting the leg valve with the ram push valve whereby in the first position of the leg valve fluid pressure is supplied to the ram push valve to urge it towards its first position.

15. A mine roof support system according to claim 14 wherein the relay has two pairs of contacts, one pair being arranged in series with the said connection means and upon being closed being adapted to pass said electrical signal to the next support in the sequence to be advanced, and the other pair being arranged in series with the solenoid of the electrohydraulic valve, the relay being such that one and only one of the two pairs of contacts is open and the other is closed in both the energised and de-ene-rgised conditions of the relay.

16. A mine roof support system according to claim 3 comprising first and second solenoid operated electrohydraulic valves, a support leg hydraulic control valve, a ram pull hydraulic control valve, and a ram push hydraulic control valve, the first electrohydraulic valve having its solenoid in series with said connection means, the

said hydraulic control valves each having first and second positions, and further comprising first fluid conduit means connecting the leg valve to the support to permit supply of pressure fluid to the support and exhaust of fluid from the support when the leg valve is in its first and second positions respectively, second fluid conduit means connecting the ram pull valve to the ram to permit exhaust of fluid on extension of the ram and supply of fluid to contract the ram in thefirst and second positions respectively of the ram pull valve, and third fluid conduit means connecting the ram push valve to the ram to permit exhaust of fluid from the ram upon contraction of the ram and supply of fluid to extend the ram in the respective first and second positions of the ram push valve, wherein a first fluid conduit is provided connecting the second electrohydraulic valve to the ram push valve whereby upon energisation of the solenoid of the latter valve pressure fluid is supplied to the ram push valve to change it from its first position to its second position.

17. A mine roof support system according to claim 16 including means for selecting any one of the supports of the sequence and for energising the solenoid of the second electrohydraulic valve mounted on said one support.

18. A mine roof support system according to claim 17 wherein the relay has two pairs of contacts, a first pair being arranged in series with the said connection means and a second pair being arranged in series with the solenoid of the first electrohydraulic valve, the relay being such that one of said pairs of contacts is open and the other of said pairs closed in both the energised and deenergised conditions of the relay, and the arrangement being such that closure of the first pair of contacts permits said electrical signal to be passed to the next support in the sequence to be advanced and closure of said second pair of contacts permits energisation of the solenoid of the said first electrohydraulic valve.

References Cited by the Examiner UNITED STATES PATENTS 3,019,776 2/1962 Clavell 91-189 3,097,829 7/1963 Seddon 261--1 3,143,862 8/1964 Cowlishaw 6195 FOREIGN PATENTS 531,230 1/1956 Canada.

SAMUEL LEVINE, Primary Examiner.

FRED E. ENGELTHALER, Examiner. P. T. COBRIN, Assistant Examiner. 

1. A MINE ROOF SUPPORT SYSTEM COMPRISING A PLURALITY OF EXTENSIBLE AND RETRACTABLE PRESSURE FLUID OPERATED MINE ROOF SUPPORTS ADAPTED TO BE ADVANCED IN A PREDETERMINED SEQUENCE AND ARRANGED AT SPACED INTERVALS ALONG A LONGWALL MINERAL FACE, AND FURTHER COMPRISING CONTROL MEANS MOUNTED ON EACH SUPPORT FOR CONTROLLING THE CYCLE OF LOWERING, ADVANCING, AND RESETTING OPERATIONS OF THE SUPPORT, EACH SAID CONTROL MEANS INCLUDING INITIATING MEANS ADAPTED AUTOMATICALLY TO INITIATE THE SAID CYCLE AND CHECK MEANS HAVING A "CLEAR" CONDITION AND A "STOP" CONDITION AND ADAPTED TO BE AUTOMATICALLY PLACED IN THE CLEAR CONDITION WHEN THE SUPPORT HAS COMPLETED THE SAID CYCLE OF OPERATION, CONNECTION MEANS ARRANGED TO CONNECT THE CONTROL MEANS FOR ONE SUPPORT TO THE CONTROL MEANS FOR THE NEXT SUPPORT IN THE SEQUENCE TO BE ADVANCED, THE CHECK MEANS ON ONE SUPPORT, THE CONNECTION MEANS, AND THE INITIATING MEANS ON THE NEXT SUPPORT IN THE SEQUENCE TO BE ADVANCED BEING DIRECTLY CONNECTED IN SERIES SO THAT UPON THE SAID CHECK MEANS BEING PLACED IN A CLEAR CONDITION AN UNBROKEN ELECTRICAL SIGNAL PATH EXISTS BETWEEN THE CONTROL MEANS FOR SAID ONE SUPPORT AND THE INITIATING MEANS FOR SAID NEXT SUPPORT IN THE SEQUENCE TO BE ADVANCED, WHEREBY THE CYCLE OF OPERATIONS FOR SAID NEXT SUPPORT IS ONLY INITIATED UPON COMPLETION OF THE CYCLE OF OPERATIONS OF SAID ONE SUPPORT. 